There have been widely used packaging machines in which packaging articles of various shapes are successively inserted within a packaging film having been shaped into a tubular form, and the longitudinal end portions of the tubular film are subjected to lengthwise sealing of the overlapping faces, followed by crosswise sealing and cutting of the tubular packaging film upon both sides or ends of each packaging article, so as to produce a number of pillow type packages. In this connection, the means for sealing the tubular packaging film in the crosswise direction (hereinafter referred to as "end sealing") is generally composed of a pair of sealers (each equipped with a cutting knife) which are disposed so as to oppose each other upon the upper and lower sides of the film feeding route.
Within a lateral pillow package making machine within which packaging articles are fed horizontally, a film is continuously fed, so that when the film is sealed and cut by means of a pair of sealers which engage the film, the movement of the sealers must be synchronized with the feeding speed of the film. Accordingly, within a rotary end sealing mechanism usually employed within such lateral pillow package making machines, nonuniform motion is imparted to the rotation of the pair of sealers so as to allow the peripheral rotational speed of the sealers during the sealing and cutting operation to be synchronized with the film feeding speed.
Within the conventional lateral pillow package making machines, the sealers for the crosswise sealing operation are adapted to be driven through means of a mechanical transmission system. Accordingly, while the rotational speed of the sealers can be mechanically controlled, it cannot be varied substantially since the variable speed range is extremely limited as shown within the graph of FIG. 6. Thus, when the height of the packaging article 10 is great, as shown, for example, in FIG. 4(b), the sealers 40 sometimes interfere with the packaging article 10 (and the film), or vice versa, that is, sometimes one of the packages interferes with the operation or movement of the end sealers. If a package is wrapped so as to have a tightly applied film 16 by controlling the packaging apparatus in such a manner that the package length may is effectively shortened, it provides a good appearance for the finished package and is also economical since the film length required for one package can be reduced. However, when the height of the packaging article is substantial, the apparatus or system is not practically operative, in that such tight packaging cannot be achieved since the tips of the sealers interfere with the rear end of the preceding packaging article or the fore end of the following packaging article, during their sealing and cutting operations.